Pressure vessels are used for storage of pressurized gases and/or pressurized liquids. For instance, pressure vessels are already being employed in natural gas-driven motor vehicles. In addition, there are known pressure vessels for motor vehicles that are filled with pressurized hydrogen. The hydrogen can be combusted with oxygen in an internal combustion engine or can react with oxygen to give water in a fuel cell, in which case the electrical energy obtained is fed to an accumulator or an electric motor.
Corresponding pressure vessels have to withstand great stresses. Pressure vessels for natural gas are filled, for example, with a pressure up to 250 bar. Pressure vessels for hydrogen are filled with up to 700 bar.
EP 0 810 081 A1 discloses a pressure vessel comprising a connecting element, and inner vessel and a support shell which surrounds the inner vessel. The connecting element comprises a neck section in the form of a sleeve and a shoulder section and is connected via its outer face to an inner face of the inner vessel. The inner vessel is bonded to the support shell in such a way that the inner vessel is arranged in a sandwich-like manner between the connecting element and the support shell in the region of the bond to the connecting element. The pressure vessel has an orifice bounded by the neck section in the form of a sleeve of the connecting element. The neck section of the connecting element also has an inner thread into which a valve unit is screwed, the latter being connectable to a supply line.
Because of the varying compressive stress on the pressure vessels, these are particularly highly stressed especially in the region of the bond of the connecting element to the inner vessel. Moreover, the pressure vessels have to withstand very high stresses especially in the case of an accident. In the case of a drop test where the pressure vessel is allowed to fall onto the connecting element, great stresses occur at the bond surface between the attachment element and the inner vessel.
In the case of the pressure vessel known from EP 0 810 081 A1, the effect of the varying compressive stress is that the bond surface between the connecting element and the inner vessel is subject to great shear forces and the connecting element can be detached relatively easily from the inner vessel. The same applies to a drop test where the pressure vessel is allowed to fall onto the attachment element. In the case of a corresponding drop test, the connecting element becomes detached relatively easily from the inner vessel, which leads to escape of the hydrogen or the natural gas from the pressure vessel. Moreover, the pressure vessel known from EP 0 810 081 A1 has the problem that, on exceedance of a particular torque which is exerted on the connecting element, the connecting element becomes detached from the inner vessel, and so hydrogen or natural gas escapes from the pressure vessel in this case too.
EP 2 573 447 A1 discloses a pressure vessel comprising a mouth member having a metallic top component, an inner vessel and a support shell which surrounds the inner vessel. The metallic top component comprises a neck section in the form of a sleeve and a surrounding flange. The surrounding flange has been provided with a surface coating arranged between the surrounding flange and a bonding component consisting of plastic. It is also possible for a bonding layer to be provided between the bonding component consisting of plastic and an inner face of the inner vessel. In addition, EP 2 573 447 A1 states that the top component can be roughened by sandblasting or shotblasting or by means of chemical surface treatment.